Anglo American Platinum - or Amplats - fell three per cent on Wednesday after wildcat strikes spread to its Union Mine in Limpopo Province, to the northwest of Rustenburg.
On Tuesday evening the firm, which accounts for around 40% of global platinum supply, said staff had reported for work but refused to go underground for their shifts.
Instead the workers presented a memorandum to the mine's management.
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The company has said it will only negotiate through official channels and obtained an injunction declaring the strike illegal
It demanded staff returned to work on Wednesday morning, but by 1600 the firm had given no further update on activity.
It also said the security situation in the Rustenburg area had worsened during Monday evening and advised employees at its Rustenburg mining operations not to attend work on Tuesday.
The company had intended to resume operations on the day shift on Wednesday morning.
Attendance at Rustenburg has been below 20% since September when the strikes began.
Industrial relations in the South African mining sector have been on a knife edge since 44 people died during violent protests at Lonmin's Marikana project in August.
At 1600 on Wednesday Amplats was trading down 3.1% at 1,813p.
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